Base for spring stool



FIG. 1 is a front elevation view of the base for spring stool illustrating my new design.

FIG. 2 is a right side elevation view thereof.

FIG. 3 is a left side elevation view thereof.

FIG. 4 is a rear elevation view thereof.

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The broken lines shown in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a base for spring stool, as shown and described. 